J. Anim Sci.
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J. Anim Sci. 1970. 30:966-969.
© 1970 American Society of Animal Science
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Influence of Programmed Circadian Temperature Changes on the Reproductive Performance of Ewes1

T. D. Rich2,3, and C. W. Alliston

Purdue University, Lafayette, Indiana4

Abstract

Numerous studies (Alliston and Ulberg, 1961; Dutt, 1963, 1964; Thwaites, 1967, 1968; Yeates, 1953) have illustrated that continuous high ambient temperatures influence the reproductive performance of ewes. In general, these reports have indicated that from beginning of estrus until ova pass into the uterus is a critical period in response to heat stress. High ambient temperature during this period has caused an increased proportion of abnormal ova shed, decreased fertilization rate and increased embryonic death early in gestation.

Recently, Thwaites (1969) reported that diurnally variable heat stress for 14 days after breeding did not significantly depress the reproductive performance of Merino ewes. This condition consisted of an 8-hr. period of 41.1 C at 40% relative humidity and a 16-hr. period of 35 C at 30% relative humidity. These conditions are more severe than those common to major sheep producing areas of the united States.

The objective of this study was to estimate the influence of a circadian fluctuating (21.1 to 32.2 C) ambient temperature upon the reproductive performance of Columbia and Rambouillet ewes.

Footnotes

1 This investigation was supported in part by Public Health Service Research Grant HD 03009-03, from the National Institute of Child Health and Human Development. Published as Journal Paper No. 3854, Purdue University Agricultural Experiment Station.

2 David Ross Fellow, Purdue Research Foundation, Grant No. 5088, Lafayette, Indiana 47907.

3 Present address: Animal Science Department, South Dakota State University, Brookings 57006.

4 Department of Animal Sciences.






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